Yours is a model 500, but I would guess it's similar to the 550 model. What that shows is that there are several thermistors that sense temps and there's also LEDs that are telltales that can be checked for trouble indications.
What I'd do first off is find a copy of the service manual for that model, then read up on the indicator LED. Get it to fault again and then check the LED(s). Which means to open the case and while in there check the electrical connections for all the thermistors making sure they are all tight
. A loose connector can throw things out of wack in the circuitry.
Anyway, somewhere to start.
You can also just google 'Mobile RV service near me' and call and ask if they have experience with your device. Always check any service company here RVServiceReviews
online first. Might have to read between the lines if there aren't many reviews though.